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  • How to manage primary key while updating [migrated]

    - by Subin Jacob
    In the following table primaryKeyColumn is primary key. To maintain the data history I always uses the values with WHERE condition(WHERE StatusColumn=1) And will set the StatusColumn to 0 if the data is edited (So that I could keep the previous data). But the problem is, if I update it to 0 , I can't insert the same key to primarykeycolumn since the column validated for primary keys. How can I manage these kind of validations? what the mistake I did in this design? primaryKeyColumn ValueColumn StatusColumn ---------------- ----------- ------------ 2 Name1 1 3 Name2 1 4 Name3 0

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  • Abstract Data Type and Data Structure

    - by mark075
    It's quite difficult for me to understand these terms. I searched on google and read a little on Wikipedia but I'm still not sure. I've determined so far that: Abstract Data Type is a definition of new type, describes its properties and operations. Data Structure is an implementation of ADT. Many ADT can be implemented as the same Data Structure. If I think right, array as ADT means a collection of elements and as Data Structure, how it's stored in a memory. Stack is ADT with push, pop operations, but can we say about stack data structure if I mean I used stack implemented as an array in my algorithm? And why heap isn't ADT? It can be implemented as tree or an array.

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  • I want to build a Virtual Machine, are there any good references?

    - by Michael Stum
    I'm looking to build a Virtual Machine as a platform independent way to run some game code (essentially scripting). The Virtual Machines that I'm aware of in games are rather old: Infocom's Z-Machine, LucasArts' SCUMM, id Software's Quake 3. As a .net Developer, I'm familiar with the CLR and looked into the CIL Instructions to get an overview of what you actually implement on a VM Level (vs. the language level). I've also dabbled a bit in 6502 Assembler during the last year. The thing is, now that I want¹ to implement one, I need to dig a bit deeper. I know that there are stack based and register based VMs, but I don't really know which one is better at what and if there are more or hybrid approaches. I need to deal with memory management, decide which low level types are part of the VM and need to understand why stuff like ldstr works the way it does. My only reference book (apart from the Z-Machine stuff) is the CLI Annotated Standard, but I wonder if there is a better, more general/fundamental lecture for VMs? Basically something like the Dragon Book, but for VMs? I'm aware of Donald Knuth's Art of Computer Programming which uses a register-based VM, but I'm not sure how applicable that series still is, especially since it's still unfinished? Clarification: The goal is to build a specialized VM. For example, Infocom's Z-Machine contains OpCodes for setting the Background Color or playing a sound. So I need to figure out how much goes into the VM as OpCodes vs. the compiler that takes a script (language TBD) and generates the bytecode from it, but for that I need to understand what I'm really doing. ¹ I know, modern technology would allow me to just interpret a high level scripting language on the fly. But where is the fun in that? :) It's also a bit hard to google because Virtual Machines is nowadays often associated with VMWare-type OS Virtualization...

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  • Builder Pattern: When to fail?

    - by skiwi
    When implementing the Builder Pattern, I often find myself confused with when to let building fail and I even manage to take different stands on the matter every few days. First some explanation: With failing early I mean that building an object should fail as soon as an invalid parameter is passed in. So inside the SomeObjectBuilder. With failing late I mean that building an object only can fail on the build() call that implicitely calls a constructor of the object to be built. Then some arguments: In favor of failing late: A builder class should be no more than a class that simply holds values. Moreover, it leads to less code duplication. In favor of failing early: A general approach in software programming is that you want to detect issues as early as possible and therefore the most logical place to check would be in the builder class' constructor, 'setters' and ultimately in the build method. What is the general concensus about this?

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  • Should these concerns be separated into separate objects?

    - by Lewis Bassett
    I have objects which implement the interface BroadcastInterface, which represents a message that is to be broadcast to all users of a particular group. It has a setter and getter method for the Subject and Body properties, and an addRecipientRole() method, which takes a given role and finds the contact token (e.g., an email address) for each user in the role and stores it. It then has a getContactTokens() method. BroadcastInterface objects are passed to an object that implements BroadcasterInterface. These objects are responsible for broadcasting a passed BroadcastInterface object. For example, an EmailBroadcaster implementation of the BroadcasterInterface will take EmailBroadcast objects and use the mailer services to email them out. Now, depending on what BroadcasterInterface implementation is used to broadcast, a different implementation of BroadcastInterface is used by client code. The Single Responsibility Principle seems to suggest that I should have a separate BroadcastFactory object, for creating BroadcastInterface objects, depending on what BroadcasterInterface implementation is used, as creating the BroadcastInterface object is a different responsibility to broadcasting them. But the class used for creating BroadcastInterface objects depends on what implementation of BroadcasterInterface is used to broadcast them. I think, because the knowledge of what method is used to send the broadcasts should only be configured once, the BroadcasterInterface object should be responsible for providing new BroadcastInterface objects. Does the responsibility of “creating and broadcasting objects that implement the BroadcastInterface interface” violate the Single Responsibility Principle? (Because the contact token for sending the broadcast out to the users will differ depending on the way it is broadcasted, I need different broadcast classes—though client code will not be able to tell the difference.)

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  • Nicest way to map rgb colors from html to led

    - by back_ache
    I have attached an rgb led to a color picker on a webpage and have hit the obvious problem that though the led is 8-bit like html the color rendition is very different so with the more subtle shades the led values for the color are wildly different to the html values. The brute-force method would be for me to have a lookup-table on the webserver to map the two sets of values but would ideally like to do it more elegantly Before I start listing all my 101 ideas for doing this I wondered if anyone else had come across the issue, the end-game would be to be able to abstract the color-rendition of different leds and make it available as a webservice (html value and device id in, led value out)

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  • How to display values from another website to an new html page?

    - by user3098728
    How to display the value in a new html file from different website? This an example field of values that need to display into new html file and I want to display the said values in the input box (Contract ID) of this page JSFiddle. I have 2 JS code that would display that values, but unfortunately its not working and I dont know how to display that value in html input box. Please help me. Thank you I want to display the said value in this input box: Here the JS file to read the values: function scanLapVerification() { try { var page_title = "Title"; var el = getElement(document, "class", "view-operator-verification-title", ""); if (!el || el.length == 0) return; if (el[0].innerText != page_title) return; var page_title = ''; var el = getElement(document, "class", "workflowActivityDetailPanel", ""); if (el && el.length > 0) { var eltr = getElement(el[0], "tag", "tr", ""); if (eltr && eltr.length > 0) { //Read Contract ID var contractId = { CI: { id: null } }; var con_id = null; for (var i = 0; i < eltr.length; i++) { tr_text = eltr[i].innerText; if (tr_text.substr(0, "Contract ID".length) == "Contract ID") con_id = "CI"; if (con_id && tr_text.substr(0, "Contract ID".length) == "Contract ID") { contractId[con_id].id = tr_text.substr("Contract ID".length + 1, tr_text.length - "Contract ID".length - 1); } } var contract_id = contractId.CI.id; return { content: "cid_check", con_id: con_id }; } return { status: "KO" }; } catch (e) { alert("Exception: scanLapVerification\n" + e.Description); return { status: "KO", message: e }; } }; And here's the 2nd JS that display to a new html page: function scanLapVerification() { chrome.tabs.sendRequest(tabLapVerification, { method: "scanLapVerification" }, function (response) { msgbox("receiveResponse: scanLapVerification " + jsonToString(response, "JSON")); //maintaining state in the background if (response.data.content == "cid_check") { //Popup window features var popupWindow = null; var name; var width = 550; var height = 200; var left = parseInt((screen.availWidth / 2) - (width / 2)); var top = parseInt((screen.availHeight / 2) - (height / 2)); var windowFeatures = "width=" + width + ",height=" + height + ",left=" + left + ",top=" + top + "screenX=" + left + ",screenY=" + top; //Input new address with popup window if (confirm("Does the client has new address?") == true) { popupWindow = window.open('/htmlname.htm', "title", windowFeatures + encodeURIComponent(response.data.contract_id)); popupWindow.focus(); } else { name = ""; } }); }

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  • How should an API use http basic authentication

    - by user1626384
    When an API requires that a client authenticates to it, i've seen two different scenarios used and I am wondering which case I should use for my situation. Example 1. An API is offered by a company to allow third parties to authenticate with a token and secret using HTTP Basic. Example 2. An API accepts a username and password via HTTP Basic to authenticate an end user. Generally they get a token back for future requests. My Setup: I will have an JSON API that I use as my backend for a mobile and web app. It seems like good practice for both the mobile and web app to send along a token and secret so only these two apps can access the API blocking any other third party. But the mobile and web app allow users to login and submit posts, view their data, etc. So I would want them to login via HTTP Basic as well on each request. Do I somehow use a combination of both these methods or only send the end user credentials (username and token) on each request? If I only send the end user credentials, do I store them in a cookie on the client?

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  • Release an upgraded iOS app with a different revenue model

    - by tassock
    I am starting a new iOS project and initially plan release a simple free version to gather feedback. I don't intend to monetize or market this initial version. However, I believe "Version 2" of this app will be good enough to pay for. I would prefer to release Version 2 as an upgrade from Version 1 rather than release it as a separate app. This way I can reserve a name for the app. It will also be easier to keep everything in a single repository. Are there any downsides of this approach? It's my understanding that I can change the price of an app at any point in time, so it shouldn't be an issue transitioning to a paid app, should it?

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  • Best method to organize/manage dependencies in the VCS within a large solution

    - by SnOrfus
    A simple scenario: 2 projects are in version control The application The test(s) A significant number of checkins are made to the application daily. CI builds and runs all of the automation nightly. In order to write and/or run tests you need to have built the application (to reference/load instrumented assemblies). Now, consider the application to be massive, such that building it is prohibitive in time (an entire day to compile). The obvious side effect here, is that once you've performed a build locally, it is immediately inconsistent with latest. For instance: If I were to sync with latest, and open up one of the test projects, it would not locally build until I built the application. This is the same when syncing to another branch/build/tag. So, in order to even start working, I need to wait a day to build the application locally, so that the assemblies could be loaded - and then those assemblies wouldn't be latest. How do you organize the repository or (ideally) your development environment such that you can continually develop tests against whatever the current build is, or a given specific build, while minimizing building the application as much as possible?

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  • Inheritance, commands and event sourcing

    - by Arthis
    In order not to redo things several times I wanted to factorize common stuff. For Instance, let's say we have a cow and a horse. The cow produces milk, the horse runs fast, but both eat grass. public class Herbivorous { public void EatGrass(int quantity) { var evt= Build.GrassEaten .WithQuantity(quantity); RaiseEvent(evt); } } public class Horse : Herbivorous { public void RunFast() { var evt= Build.FastRun; RaiseEvent(evt); } } public class Cow: Herbivorous { public void ProduceMilk() { var evt= Build.MilkProduced; RaiseEvent(evt); } } To eat Grass, the command handler should be : public class EatGrassHandler : CommandHandler<EatGrass> { public override CommandValidation Execute(EatGrass cmd) { Contract.Requires<ArgumentNullException>(cmd != null); var herbivorous= EventRepository.GetById<Herbivorous>(cmd.Id); if (herbivorous.IsNull()) throw new AggregateRootInstanceNotFoundException(); herbivorous.EatGrass(cmd.Quantity); EventRepository.Save(herbivorous, cmd.CommitId); } } so far so good. I get a Herbivorous object , I have access to its EatGrass function, whether it is a horse or a cow doesn't matter really. The only problem is here : EventRepository.GetById<Herbivorous>(cmd.Id) Indeed, let's imagine we have a cow that has produced milk during the morning and now wants to eat grass. The EventRepository contains an event MilkProduced, and then come the command EatGrass. With the CommandHandler, we are no longer in the presence of a cow and the herbivorious doesn't know anything about producing milk . what should it do? Ignore the event and continue , thus allowing the inheritance and "general" commands? or throw an exception to forbid execution, it would mean only CowEatGrass, and HorseEatGrass might exists as commands ? Thanks for your help, I am just beginning with these kinds of problem, and I would be glad to have some news from someone more experienced.

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  • Work Item Traceability in TFS 2010

    - by Sam Patrick
    I have created a Windows Form project (VS solution) under a TFS 2010 project. I may eventually add more solutions to the TFS project. My question: Can we create a Use Case WIT for a specific solution within a TFS project? Furthermore, is it possible to create a "traceability matrix" that starts at the Use Case level and goes down to the the code level (at least the namespace level) of that particular VS solution?

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  • Should I update blog posts or rewrite them as technology (and me) changes?

    - by Rachel
    I started a programming blog earlier this year, and since I started it some things have changed. Some changes are due to technology changing, some changes are due to my code libraries improving, and some (ok, probably most) are due to me changing as I learn more. I want to go back and completely re-write certain blog posts. Is it better to rewrite posts to remove old information and update them with new stuff, or to create entirely new posts and possibly take down old ones? I'm not talking about small changes to the code, or an extra few sentences, but complete rewrites with new code, new information, etc. Some things to consider are comments on the post, subscribers who receive updates when new posts are created, and user bookmarks.

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  • How does the ? make a quantifier lazy in regex

    - by Uriel Katz
    I've been looking into regex lately and figured that the ? operator makes the *,+, or ? lazy. My question is how does it do that? Is it that *? for example is a special operator, or does the ? have an effect on the *? In other words, does regex recognize *? as one operator in itself, or does regex recognize *? as the two separate operators * and ?? If it is the case that *? is being recognized as two separate operators, how does the ? affect the * to make it lazy. If ? means that the * is optional, shouldn't this mean that the * doesn't have to exists at all. If so, then in a statement .*? wouldn't regex just match separate letters and the whole string instead of the shorter string? Please explain, I'm desperate to understand.

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  • Unit testing in Django

    - by acjohnson55
    I'm really struggling to write effective unit tests for a large Django project. I have reasonably good test coverage, but I've come to realize that the tests I've been writing are definitely integration/acceptance tests, not unit tests at all, and I have critical portions of my application that are not being tested effectively. I want to fix this ASAP. Here's my problem. My schema is deeply relational, and heavily time-oriented, giving my model object high internal coupling and lots of state. Many of my model methods query based on time intervals, and I've got a lot of auto_now_add going on in timestamped fields. So take a method that looks like this for example: def summary(self, startTime=None, endTime=None): # ... logic to assign a proper start and end time # if none was provided, probably using datetime.now() objects = self.related_model_set.manager_method.filter(...) return sum(object.key_method(startTime, endTime) for object in objects) How does one approach testing something like this? Here's where I am so far. It occurs to me that the unit testing objective should be given some mocked behavior by key_method on its arguments, is summary correctly filtering/aggregating to produce a correct result? Mocking datetime.now() is straightforward enough, but how can I mock out the rest of the behavior? I could use fixtures, but I've heard pros and cons of using fixtures for building my data (poor maintainability being a con that hits home for me). I could also setup my data through the ORM, but that can be limiting, because then I have to create related objects as well. And the ORM doesn't let you mess with auto_now_add fields manually. Mocking the ORM is another option, but not only is it tricky to mock deeply nested ORM methods, but the logic in the ORM code gets mocked out of the test, and mocking seems to make the test really dependent on the internals and dependencies of the function-under-test. The toughest nuts to crack seem to be the functions like this, that sit on a few layers of models and lower-level functions and are very dependent on the time, even though these functions may not be super complicated. My overall problem is that no matter how I seem to slice it, my tests are looking way more complex than the functions they are testing.

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  • How do I overcome paralysis by analysis when coding?

    - by LuxuryMode
    When I start a new project, I often times immediately start thinking about the details of implementation. "Where am I gonna put the DataBaseHandler? How should I use it? Should classes that want to use it extend from some Abstract superclass..? Should I an interface? What level of abstraction am I going to use in my class that contains methods for sending requests and parsing data?" I end up stalling for a long time because I want to code for extensibility and reusability. But I feel it almost impossible to get past thinking about how to implement perfectly. And then, if I try to just say "screw it, just get it done!", I hit a brick wall pretty quickly because my code isn't organized, I mixed levels of abstractions, etc. What are some techniques/methods you have for launching into a new project while also setting up a logical/modular structure that will scale well?

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  • Any valid reason to Nest Master Pages in ASP.Net rather than Inherit?

    - by James P. Wright
    Currently in a debate at work and I cannot fathom why someone would intentionally avoid Inheritance with Master Pages. For reference here is the project setup: BaseProject MainMasterPage SomeEvent SiteProject SiteMasterPage nested MainMasterPage OtherSiteProject MainMasterPage (from BaseProject) The debate came up because some code in BaseProject needs to know about "SomeEvent". With the setup above, the code in BaseProject needs to call this.Master.Master. That same code in BaseProject also applies to OtherSiteProject which is just accessed as this.Master. SiteMasterPage has no code differences, only HTML differences. If SiteMasterPage Inherits MainMasterPage rather than Nests it, then all code is valid as this.Master. Can anyone think of a reason why to use a Nested Master Page here instead of an Inherited one?

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  • c# class naming standards/guidelines

    - by Ben
    Over the years I've used various naming conventions for services in my applications for example: [ClassName]Service [ClassName]Manager [ClassName]Factory [ClassName]Provider [ClassName]Helper I generally only use the "Helper" suffix for utility classes that have no external dependencies. However I find that there is a bit of a cross-over between the others, and wondered if there was any recommendations/standards/guidelines on what to use and when?

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  • What are some good Photo and Artwork APIs?

    - by Ryan T
    We had an idea for starting a ecards service and were looking into the possibility of populating our site using photo/artwork APIs. Due to legal reasons, Flikr probably won't work, although I've started to scour the web for other options. Basically we just need two functions the user should be able to browse the site's collection and choose a picture we should be able to recall and render a specific picture on our site. From there we should have no problem building our application. The main obstacle is that we're lacking content at the moment. I haven't been able to find too many examples of this being done, so I was wondering if anyone here might know people who have done something similar to what we're trying to do, or know of any leads that might be able to help us out. Suggestions for other APIs that are out there, or forums/communities that might be able to point us in the right direction are also welcome.

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  • unseen/unknown function definition in linux source

    - by Broncha
    Can any one please explain this piece of code I found in the linux kernel source. I see a lots of code like this in linux and minix kernel but dont seem to find what it does (even if C compilers support that kind of function definition) /* IRQs are disabled and uidhash_lock is held upon function entry. * IRQ state (as stored in flags) is restored and uidhash_lock released * upon function exit. */ static void free_user(struct user_struct *up, unsigned long flags) __releases(&uidhash_lock) { uid_hash_remove(up); spin_unlock_irqrestore(&uidhash_lock, flags); key_put(up->uid_keyring); key_put(up->session_keyring); kmem_cache_free(uid_cachep, up); } I cannot find out if this reference __releases(&uidhash_lock) before the parenthesis starts is allowed OR supported. (It sure is supported as it is in the linux kernel)

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  • How should calculations be handled in a document database

    - by Morten
    Ok, so I have a program that basically logs errors into a nosql database. Right now there is just a single model for an error and its stored as a document in the nosql database. Basically I want to summarize across different errors and produce a summary of the "types" of errors that occured. Traditionally in a SQL database the this normalization would work with groupings, sums and averages but in a NoSQL database I assume I need to use mapreduce. My current model seems unfit for the task, how should I change the way I store "models" in order to make statistical analysis easy? Would a NoSQL database even be the right tool for this type of problem? I'm storing things in Google AppEngine's BigTable, so there are some limitations to think of as well.

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  • Author has inserted copyright into code with gnu public license notice - implications?

    - by Nicholas Pickering
    I've found a project on Github that I'm interested in contributing to which claims to be open source and has a GPL license included with it. But the original author has added a copyright notification to each source file. I'm not sure why but I don't feel right contributing to a project that's always going to have someone else's name on it. It really breaks the community-created feel, and makes me uneasy about what the author might choose to do with the project next. What are the implications of copyrighting open source GPL code as so? What power does this give the original author over a contributor? # Copyright (C) 2012, 2013 __AUTHORNAME__ # This file is part of __PROJECTNAME__. # # __PROJECTNAME__ is free software: you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation, either version 3 of the License, or # (at your option) any later version. # # __PROJECTNAME__ is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License

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  • Developing an internet-enabled application as a Kiosk on Windows 7

    - by maple_shaft
    I am finalizing development of a desktop Java application that communicates with an outside web server, and now I need to start seriously considering deployment. This application will run on a large touchscreen all-in-one workstation running Windows 7. It will be located in a public-area and thus must be LOCKED-DOWN Hanibal Lecter style. Early in the project nobody really concerned themselves with this fact just assuming that we can buy some magical software for Windows 7 that will automatically take care of all this, however I am finding now that this looks to be a LOT more complicated than my manager ever thought. I need to: - Lock down the standard hot-keys (ALT+TAB, ALT+CTRL+DEL, etc...) Prevent the user from opening ANY programs other than the kiosk application and its spawned executables Prevent the user from closing the application Start the kiosk application on startup (this can be done without kiosk software) Auto-login to Windows on reboot (Windows Updates, power failure, bratty kid pressing the power button, etc...) Administrator passcode escape sequence for routine maintenance by desktop support professionals. To my dismay I am having a really hard time finding software that contains the whole package and am finding numerous swaths of competing information on the best way to do this. I am not necessarily looking for free or open source software and am willing to pay for software that can help me achieve this. Have any of you ever wrote kiosk software before and if so what approaches have you taken to do this?

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  • Books or help on OO Analysis

    - by Pat
    I have this course where we learn about the domain model, use cases, contracts and eventually leap into class diagrams and sequence diagrams to define good software classes. I just had an exam and I got trashed, but part of the reason is we barely have any practical material, I spent at least two good months without drawing a single class diagram by myself from a case study. I'm not here to blame the system or the class I'm in, I'm just wondering if people have some exercise-style books that either provide domain models with glossaries, system sequence diagrams and ask you to use GRASP to make software classes? I could really use some alone-time practicing going from analysis to conception of software entities. I'm almost done with Larman's book called "Applying UML and Patterns An Introduction to Object-Oriented Analysis and Design and Iterative Development, Third Edition". It's a good book, but I'm not doing anything by myself since it doesn't come with exercises. Thanks.

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  • Python: Future as a major programming language?

    - by chrisw
    After reading some Python material and seeing some Python code a few years back I decided to give it a whirl. I decided to start with Python to solve the problems on ProjectEuler.net and was throughly impressed with the language. Since then I've went on to learn Django, and now use it primarily for my web applications. I would love to have a career programming in this language, however I fear the future of the language is currently in a state of uncertainness. With Google and other major companies embracing it there may be some hope, what are your thoughts on Python, do you see many job opportunities out there?

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